The present invention relates to an image formation method, a decorative sheet, a decorative sheet molding, a process for producing an in-mold molded product, an in-mold molded product, and an ink set.
As image recording methods for forming an image on a recording medium such as paper or plastic based on an image data signal, there are an electrophotographic system, sublimation type and melt type thermal transfer systems, a screen printing system, an inkjet system, etc. The electrophotographic method has the problem that it requires a process of forming an electrostatic latent image on a photosensitive drum by charging and exposure; the system becomes complicated, and as a result the production cost becomes high. The thermal transfer method has the problem that, although the equipment is inexpensive, due to the use of an ink ribbon the running cost is high, and waste material is generated. Screen printing has the problem that the cost increases due to the necessity for plate making or printing plate making, the exchange of plate and ink, and frequent setup operations such as setting of printing conditions.
On the other hand, with regard to the inkjet system, the printing equipment is inexpensive, it is not necessary to use a plate when printing, and since an image is formed directly on a recording medium by discharging an ink composition only on a required image area, the ink composition can be used efficiently and the running cost is low, particularly in the case of small lot production. Furthermore, there is little noise and it is excellent as an image recording system, and has been attracting attention in recent years.
Among them, an inkjet recording ink composition (radiation-curing inkjet recording ink composition), which is curable upon exposure to radiation such as UV rays, is an excellent system from the viewpoint of it being possible to print on various types of substrates because, compared with a solvent-based ink composition, the drying properties are excellent and an image is resistant to spreading since the majority of the components in the ink composition cure upon exposure to radiation such as UV rays.
It is also possible to produce a molding using the inkjet method using this radiation curable inkjet ink. One example of the molding includes a molding produced by forming an ink image on a plastic medium, irradiating it with actinic radiation to thus cure the image, and then heating and softening the substrate to thus freely change the shape.
A conventional 3D plastic molding is usually produced by an image formation process that involves screen printing and then subjecting it to vacuum forming (ref. e.g. JP-A-2002-273830). On the other hand, processes for producing a plastic molding using an inkjet method have been developed in recent years (ref. e.g. JP-A-2009-185186, JP-A-2010-235697, JP-A-2009-209353, JP-A-2011-225824, JP-A-2008-087244).